Back then, the sun flung a giant plume of magnetized plasma out into space. The coronal mass ejection (CME), the sibling of a massive solar flare, traveled the 93 million miles between the Sun and Earth in only 17.6 hours. Today, it’s known as the Carrington Event and is remembered by the largest geomagnetic storm in the history of recorded space weather.

No other storm has matched it in speed or magnitude. When the shock wave of accelerated particles arrived on September 1, 1859, the disturbances to Earth’s magnetosphere were so great that telegraph communications across Europe and North America went on the fritz. Sparks leaped from the telegraph infrastructure, and machinery was so inundated with electric currents that operators were able to transmit messages while disconnected from battery power. Compasses even wiggled, and brilliant auroras were reportedly seen as far south as the Caribbean.